In coal-fired steam generators, it is necessary to provide the means for handling and disposing of the large amount of ash created in the furnace. One present day means is by continuously removing ash and slag by gravity through an opening in the furnace bottom. The ash falls into a water-filled tank, and is continuously removed therefrom by means of a submerged scraper conveyor.
A water seal is generally provided to isolate the atmosphere from the furnace interior. This consists of a plate extending down and surrounding the furnace bottom opening, which plate extends into the water-filled tank thus forming a water seal. This type of seal is provided because it allows the furnace to grow relative to the submerged scraper conveyor unit caused by thermal expansion. Large furnaces are generally top-supported so that they are free to expand in a downward direction when the unit is first started up. This growth can be on the order of 10-12 inches from the cold to the hot condition. The above provides the problem of how to be able to economically continue to operate the steam generator when the submerged scraper conveyor unit breaks down and is in need of repair.
One arrangement for overcoming the above is by providing a tank having two side-by-side conveyors in it. When one breaks down, the tank can be moved a short distance and the other conveyor is put into operation. Such apparatus is shown in U.S. Pat. No. 4,301,746. The present invention is a simple, more reasonably priced unit, which has improvements over the apparatus shown in the above patent.